[Crash-utility] [PATCH v4 2/4] Get the absolute value of SYMNAME_HASH_INDEX

[lijiang]

> > > Currently, the macro is used twice in the symbols.c. This change seems
> > > not complicated. Any thoughts?
> >
> > do I understand your suggestion correct, you propose to replace the
> >
> >         #define SYMNAME_HASH_INDEX(name) ...
> >
> > in defs.h by something like
> >
> >         static unsigned long long SYMNAME_HASH_INDEX(const unsigned char * const name) {
> >                 return (name[0] ^ (name[strlen(name)-1] * name[strlen(name)/2]) % SYMNAME_HASH);
> >         }
> >
> > in symbols.c? If so, I think that should be fine.
> >
Yes, you are right, Philipp.

>
> Please correct me if I'm wrong. I don't think the function can work.
> Let's say name[0] ^ (name[strlen(name)-1] * name[strlen(name)/2]) ==
> -1, then we will have:
>
> static unsigned long long SYMNAME_HASH_INDEX(const unsigned char * const name) {
>         return (-1) % 512;
> }
>
> The returned value is a very large number, and will overflow the array.
>
No, this is a modulo operation, and its result will never exceed '512' anyway.
(unsigned long long)(-1) % 512 = 511

Thanks.
Lianbo